A CPU embedded in an electronic apparatus such as a computer generates heat when operating. Temperature may rise to an excessive level unless the CPU is cooled. An increase in the temperature of the CPU affects the performance and service life of the computer. Cooling the CPU is thus desirable for the purpose of suppressing a temperature increase.
In a liquid cooled computer, a CPU (i.e., coolant distribution unit) serving as a liquid coolant circulating apparatus circulates coolant water to a cooling plate disposed on the CPU, thereby cooling the CPU by use of the coolant water.
In order to improve cooling ability for the purpose of cooling a CPU that generates a large amount of heat, the amount of coolant water may be increased, or the temperature of the coolant water may be decreased. However, increasing the amount of coolant water may cause erosion corrosion in the cooling plate and pipes, and may also increase load on the coolant water pump. Further, decreasing the temperature of coolant water may cause dew condensation on the cooling plate and pipes. Dew condensation on a system board may cause short-circuiting, and thus poses a risk of damaging the computer.
In consideration of the above, a cooling structure may be configured such that a thermally conductive rod provided on a cold plate having coolant pathways therein is pressed against an integrated, circuit by a spring force, thereby efficiently transmitting heat from the integrated circuit to the cold plate through the thermally conductive rod (see Japanese Laid-open Patent Publication No. H1-124300, for example).
Generally, a CPU is mounted on a substrate such as a system board. In a structure that cools a CPU by providing a cooling plate on the front surface of the system board, provision may be made such that a cooling plate is also provided on the back surface of the system board to cool the CPU from the back side thereof. Providing two cooling plates for a single system board entails the necessity to secure a sufficiently large space that can accommodate the additional cooling plate. This means a decrease in the number of system boards implemented in a single apparatus.
Further, the configuration in which the system board is placed between the two cooling plates poses a risk of being unable to perform maintenance work such as adjusting or replacing an electronic component or the like on the system board. Moreover, as inevitable consequences, the cost of the additional cooling plate serves to increase the cost of the system board or the electronic apparatus.